Nice looking boat, good equipment list with hardtop and pulpit. As mentioned, the SWSII motor is a gas and oil hog compared to the newer technology, and engine hours would have a very large influence on the boat's value since it alone can represent half the value.
A "four door" Wrangler I assume is one of the new Jeeps. It will tow a boat like this across town to a launch ramp but not across the county or in any hilly country. These boats are HEAVY on a trailer, and the hardtop adds a LOT of windage. Consider a 3/4 ton pickup for a tow vehicle. I use a Duramax, and although it's a bit overkill I don't worry about grades and can freeway it at 60-65 and get 14mpg. You are looking at about 5000-5500lbs on that trailer, an aluminum trailer saves about 400lbs. Doesn't sound like much, but a 6-7000lb tow rating for any vehicle is going to feel taxed beyond comfort.
It's still probably a reasonable deal, it's not a steal-deal, and we're telling you all this stuff so you go in with your eyes open. $18K would be a steal-deal but it would probably sell before it sat around long enough for the seller to get soft on his price. Consider that you could be faced with a repower down the road, either by necessity or by choice. A new four-stroke is $10-15K.
Survey - definitely
Four seasons use should mean the motor has about 500 hours. Ring-free isn't so critical for this model as it doesn't have the o2 sensors. Still helps with carbon on the pistons and ring grooves though. A good engine survey will tell you what you need to know.
I didn't see pics or mention of isenglass. Something I would want with a hardtop, and they can be expensive to buy or replace. In fact, most everything that needs to be replaced on a Grady is expensive :wink: However they are terrific boats.